| Abstract: | The eyes of the nudibranch mollusc Hermissenda contain 2 classes of photoreceptors. Type B photoreceptors exhibit increased light responses (LRs) and membrane excitability after repeated pairings of light and rotation and play an important role in the mediation of associatively produced reductions in phototactic behavior. Type A photoreceptors (TAPs) have also been shown to change with associative training. In previous research it was not possible to determine whether the effects of associative training reflected changes in synaptic input to TAPs or intrinsic changes in somatic conductances. In the present study, intracellular recordings from synaptically isolated TAPs were obtained on retention days after training, and pairing-specific decreases in light-induced generator potentials and decreases in resting input resistance were observed. Current- and voltage-clamp analysis of TAPs from untrained animals revealed that an important determinant of the steady-state LR was a calcium-activated K+ current (IK–Ca). Thus, TAPs also appear to be a primary site for associative information storage in Hermissenda. It is suggested that enhancement of IK–Ca by associative training may contribute to the diminished LR of TAPs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
